THE EFFECTS OF GALLIC ACID ON CARDIO-PULMONARY OXIDATIVE AND PROINFLAMMATORY RESPONSE INDUCED BY DIESEL EXHAUST PARTICLE

Abstract

Particulate matter has been known for deleterious effects on human health, one of its major toxicants, diesel exhaust particle (DEP). Studies have shown that the mechanism of action with which DEP exerts cellular damage is by inducing the generation of free radicals and reactive oxygen species that often result to oxidative stress and inflammatory responses due to the release of cytokines. This study was carried out to assess the effects of Gallic acid on cardio-pulmonary oxidative and pro-inflammatory response induced by diesel exhaust particle (DEP). The DEP was collected at Ore Motor Park then extracted and fractionated and characterized using methanol for both extraction and Gas Chromatography/Mass Spectrophotometry (GCMS) characterization. Dithiothreitol oxidation potential was used to determine the oxidative potential of the DEP in-vitro. For animal studies, 30 male albino rats weighing between 85 g and 100 g were distributed into six groups of five animals per group and were placed under treatment as follows; Group 1 was given saline and Dimethyl sulfoxide (DMSO) vehicle as control, Group 2 and 3 was given mDEP (30 and 60 μg/kg respectively) for a week (thrice a week) in the first week, Group 4 was treated with gallic acid (20 mg/kg) alone in the second week (7 days/week), Group 5 was exposed to mDEP (30 μg/kg) for a week (thrice a week) in the first week and treated with gallic acid (20 mg/kg) for 1 week (7 days per week) in the second week. Group 6 was exposed to mDEP (60 μg/kg) for a week (thrice a week) in the first week and treated with gallic acid (20 mg/kg) for 1 week (7 days per week) in the second week. All the animals had equal access to feeds and water ad libitum and the treatments lasted for two weeks. The DEP was administered nasally while the Gallic acid via intraperitoneal route. After the second week of treatment, the animals were sacrificed after the last dose of Gallic acid and blood was collected from the heart, the serum was collected and kept at -20°C. Specific organs (Lung and Heart) were aspetically removed and stored at -80°C freezer for further studies. Lactate dehydrogenase (LDH) and activated n-acetyl creatine kinase (CK-NAC) were used to assess the extent of tissue damage. Serum high density lipoprotein (HDL), Low density lipoprotein (LDL), triglycerides (TG), and total cholesterol were used to assess the effects of DEP on lipid profile. Malondialdehyde (MDA), conjugate dienes (CD), reduced glutathione (GSH), gluthathione peroxidase (GPX), glutathione reductase (G-red), catalase (CAT), superoxide dismutase (SOD) were used to assess oxidative damage. The gene expressions (at mRNA level) of protein that are tissue specific for the Lung: Surfactant protein A and D (SP-A and SP-D), and for the heart: endothelial nitrogen oxide synthetase (eNOS), cardial troponin I (CTNI) and angiotensin converting enzyme (ACE) were determined by RT-PCR. For both tissues PCSK9 involved in lipid homeostasis, pro-inflammatory genes (NFkB, TNFα & IL-8) and oxidative stress (NrF2 & HO1) genes were determined by reverse transcription and polymerase chain reaction (PCR) methods. The results show that LDH, CD, MDA, GPX levels were (p<0.001) significantly increased in the serum, while G-red, CK-NAC, CAT, SOD, GSH (p<0.001) significantly decreased in the serum when compared to control. The results of gene expressions showed that mDEP caused a significant (p<0.001) increase in the expression of pro-inflammatory genes (NF-kB, IL-8, TNFα) and PCSK9 genes but significantly (p<0.001) reduced antioxidant (Nrf2, HO1) and anti-inflammatory (IL-10) mRNA levels when compared to control. The therapeutic treatment with Gallic acid 20 mg/kg ameliorated significantly (p<0.001) all the adverse effects caused by DEP exposure. Conclusively, Gallic acid has a therapeutic potential against DEP-induced oxidative stress and inflammation and also it may serve as an agent against particulate matter induced cardio-pulmonary toxicity.